Abstract of Objectives: The overall objectives of this research are to describe the biosynthesis of lung proteoglycans and to reveal whether distinctive associations occur within the proteoglycans or between proteoglycans and collagen. From this, the long term goal of assigning a function to long proteoglycans will be facilitated and the regulation of their synthesis will be better understood. More specifically, perfused lung preparations will be used to study the biosynthesis of glycosaminoglycans of parenchymal tissue. This will generate descriptive background with which to relate the rate of synthesis of different glycosaminoglycans and the synthesis of different proteoglycan pools. Distinct proteoglycan pools will be defined by extraction techniques. Variation in synthetic rates within pools because of some association processes will be studied by density gradient fractionation. Since these experiments will be done on fetal, early postnatal, weanling and adult rabbits, they will also describe the effects of developmental factors on glycosaminoglycan and proteoglycan biosynthesis. The biosynthesis of collagen will be related to the biosynthesis of glycosaminoglycans and proteoglycans using lungs derived from rabbits of different ages. The effect of beta-D-xylosides on the biosynthesis of proteoglycans will be studied in perfused lung and/or lung explants. The possibility that collagen synthesis is also affected under conditions which cause disruptive synthesis of proteoglycans will be investigated.